A typical domestic electric clothes dryer exhausts about 150 cfm of hot moisture-laden air to the outside at a temperature of about 135.degree. F. (about 20,000 BTU/hr.) which during the winter heating season means that 150 cfm of cold outside air drawn indoors as make-up air which is first heated to room temperature by the main heating furnace and is then further heated by the clothes dryer to evaporate water from the clothes therein.
It has been proposed as in Hartung U.S. Pat. No. 3,716,925, granted Feb. 20, 1973, to provide a humidifier attachment for a clothes dryer in the form of a length of metallic vent pipe having an opening through its side wall which opens into a humidifier chamber defined between spaced-apart eccentric rings welded to the vent pipe and within a screen-supported annular filter blanket secured between the spaced-apart rings. Pivotally mounted in the vent pipe is a damper which either closes the side wall opening of the vent pipe for venting the dryer outdoors through the vent pipe or closes the downstream end portion of the vent pipe so that the dryer exhaust is conducted into the humidifier chamber through the side wall opening of the vent pipe. The damper is operated by a rod connected to the damper and extending exteriorly of the humidifier chamber between the ends of the annular filter blanket which are folded in over an axial gap in the supporting screen. In the use of this humidifier attachment, the hot moisture-laden air from the dryer flows into the humidifier chamber and is discharged into the laundry room in all directions including the wall behind the dryer.
Moreover, the proposed humidifier attachment is quite heavy and bulky and is expensive to manufacture and does not lend itself for suspension from plastic vent hose which is in prevalent use in conjunction with electric clothes dryers.